Thread: Mysteries Of Discovery 4 Electrics

That is the battery monitor which measures the current flow in/out of the battery to determine what voltage the ECU should tell the alternator to run at, based on need and time to recharge (effectively). This is to reduce load on the engine from the alternator and supposedly improve the battery health (but seemingly it’s quite the opposite as it will sacrifice the battery charging for engine efficiency).

If that things isn’t seeing the correct data because of a bad wire, then it makes sense it wouldn’t charge correctly.

What was the error code in the ECU? Did you check it or just assume an alternator issue because of the triangle?

Originally Posted by DiscoJeffster

That is the battery monitor which measures the current flow in/out of the battery to determine what voltage the ECU should tell the alternator to run at, based on need and time to recharge (effectively). This is to reduce load on the engine from the alternator and supposedly improve the battery health (but seemingly it’s quite the opposite as it will sacrifice the battery charging for engine efficiency).

If that things isn’t seeing the correct data because of a bad wire, then it makes sense it wouldn’t charge correctly.

What was the error code in the ECU? Did you check it or just assume an alternator issue because of the triangle?

Thanks this confirms what my research revealed.

My Carsoft Scanner reported Error P0A1A.

My issue is what is the reason for those inflexible sections in the wire, how could removing and refitting the original alternator compromise this measurement circuitry? Alright I admit to breaking the LEN connection wire on the alternator however this was repaired, extended to make subsequent alternator removals simpler, it appears there is no finite logic to what has occurred here.

Owners have requested a means to get back to basic alternators and control circuitry, to date I have not seen a solution. I personally am a believer in "if it aint broke dont fix it" however I do practice preventive maintenance.

You may have bumped the wire while removing the negative terminal, otherwise pure co-incidence.

Edit: I removed the back cover from my recently dead 220A L322 alternator to find a pair of cooked diodes and the ends of the respective field wires burnt. No sense in fitting a new diode pack.

Originally Posted by Graeme

You may have bumped the wire while removing the negative terminal, otherwise pure co-incidence.

Edit: I removed the back cover form my recently dead 220A L322 alternator to find a pair of cooked diodes and the ends of the respective field wires burnt. No sense in fitting a new diode pack.

Graeme you have probably nailed it. Be nice if there was an error to identify when this circuit is compromised.

P0A1A Details as per the Service Manual

Generator Control Module -
No sub type information
Generator to engine
control module LIN
circuit, open circuit
Generator/engine
control module failure
Check for good/clean contact at
generator and engine control module
LIN circuit connectors/pins. Refer to the
electrical circuit diagrams and check
generator to engine control module LIN
circuit for open circuit. Check for
engine control module hardware DTCs
and refer to relevant DTC index. Clear
DTCs and repeat automated diagnostic
procedure using the manufacturer
approved diagnostic system
Check and install a new generator /
http://www.landrover-manuals

Originally Posted by Gravy

I had previously cleaned the ring terminal attached to the battery post, however never given it a tug to ensure it was not severed. Also never had the battery positive terminal disconnected, as recommended I always disconnected the negative terminal prior to working on the vehicle.

This is where the mystery makes its appearance, the wire in my case was not severed, however along its length there are a series of sections clothed with heat shrink which are tough to flex, their purpose can not be identified.

Since flexing these Joints (????) the red battery symbol has disappeared. Engine running after cranking provides a battery terminal voltage of 14.6 or 14.7 Volts.

If anyone can explain what has happened here I would gladly offer my stripped down original alternator as a reward.

Is that wire Brown with a blue stripe? If so it's the positive supply to the battery monitor module and has 2 solder joints which would likely be the heatshrink sections. According to the wiring diagram it's 1mm from the battery to a 0.35mm section and then back to 1mm before it gets to the BMS module. A dodgy solder joint would result in the "it wasn't working until I flexed it" kind of symptom.
The BMS module communicates with the BCM on a LIN bus, and that would cease if the BMS lost its supply.

Page 90 of the D4 wiring diagram 414-02 - Generator and Regulator. DV6 3.0L.

Originally Posted by BradC

Is that wire Brown with a blue stripe? If so it's the positive supply to the battery monitor module and has 2 solder joints which would likely be the heatshrink sections. According to the wiring diagram it's 1mm from the battery to a 0.35mm section and then back to 1mm before it gets to the BMS module. A dodgy solder joint would result in the "it wasn't working until I flexed it" kind of symptom.
The BMS module communicates with the BCM on a LIN bus, and that would cease if the BMS lost its supply.

Thanks for this solution

Page 90 of the D4 wiring diagram 414-02 - Generator and Regulator. DV6 3.0L.

Is there a reason behind the wire diameter changes? Is it to create a fusible link as on previous models there was a fuse in LIN bus circuit (Fuse 20).

Looks like I might have to resolder these joints to be certain the fault wont be duplicated.

Not that I can tell. The wiring diagram just shows 3 segments with 2 solder joints. The segment in the middle is 0.35mm.

I don't have a D4, just the wiring diagram.

My D3 is "not quite" as complex (marginally) but can still be as problematic!

If you have the dreaded RED BATTERY SYMBOL making its appearance on your dash confirm the integrity of the conductor between the positive battery terminal and the Battery Monitor Module.

As has been posted this wire has two joins in it where the wire gauge undergoes changes. These joins are only crimped and the quality of the joins is poor. If there is any doubt remove the hot melt filled heat shrink, cut, strip, solder and heat shrink the wire joints.

Might save you from the grief, worry and expense I have experienced.